CVE-2026-74496

fou: Fix use-after-free in fou_create()

State: Published
Severity: 7.8 High
Published: Aug 15, 2026
Updated: Oct 16, 2026
Reserved: Aug 15, 2026

Description

In the Linux kernel, the following vulnerability has been resolved:

fou: Fix use-after-free in fou_create()

fou_create() publishes struct fou through sk_user_data before adding the new FOU port to the per-netns list. If fou_add_to_port_list() fails, the error path frees fou while it is still reachable through sk_user_data. A concurrent receive can then dereference the freed object in fou_from_sock().

This ordering issue was previously noted in the linked discussion.

The failure is reachable when local port 0 is requested. Each socket binds to a different ephemeral port, but fou_cfg_cmp() compares the requested port 0 and reports -EALREADY once an entry already exists.

Release the tunnel socket before freeing fou so sk_user_data is cleared first, and defer reclamation with kfree_rcu() to protect concurrent RCU readers. This matches the lifetime handling in fou_release().

Scores

CVSS	Score	Vector	Source
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	23461551c00628c3f3fe9cf837bf53cf8f212b63 to before 0ee628a58d83e571f36ec9f07624d6845e420c50Affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 to before a6fca682cfa2041e31aa72cc397c4a1406eb7468Affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 to before b3f9c3e60aa25453774f899d25b5e61dd0bec1d5Affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 to before 99f4d3120b244f92e5df787152041296a2860cb5Affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 to before 58835985c035a8333742f829ad7e0889a082f9d3Affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 to before 9042867d4701728f0c6527215b11471759904d8fAffected 23461551c00628c3f3fe9cf837bf53cf8f212b63 to before a28d8903bfe76089ea4bbdbff9976965f9ef8107Affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 to before b14361aca6350ff7907b0e9903c7b94dc7d5d4a0Affected
LinuxLinux	3.18Affected before 3.18Not affected 5.10.271 through 5.10.Not affected 5.15.222 through 5.15.Not affected 6.1.189 through 6.1.Not affected 6.6.158 through 6.6.Not affected 6.12.111 through 6.12.Not affected 6.18.53 through 6.18.Not affected 7.1.8 through 7.1.*Not affected 7.2 and laterNot affected

Product

Versions

LinuxLinux

23461551c00628c3f3fe9cf837bf53cf8f212b63 to before 0ee628a58d83e571f36ec9f07624d6845e420c50Affected
23461551c00628c3f3fe9cf837bf53cf8f212b63 to before a6fca682cfa2041e31aa72cc397c4a1406eb7468Affected
23461551c00628c3f3fe9cf837bf53cf8f212b63 to before b3f9c3e60aa25453774f899d25b5e61dd0bec1d5Affected
23461551c00628c3f3fe9cf837bf53cf8f212b63 to before 99f4d3120b244f92e5df787152041296a2860cb5Affected
23461551c00628c3f3fe9cf837bf53cf8f212b63 to before 58835985c035a8333742f829ad7e0889a082f9d3Affected
23461551c00628c3f3fe9cf837bf53cf8f212b63 to before 9042867d4701728f0c6527215b11471759904d8fAffected
23461551c00628c3f3fe9cf837bf53cf8f212b63 to before a28d8903bfe76089ea4bbdbff9976965f9ef8107Affected
23461551c00628c3f3fe9cf837bf53cf8f212b63 to before b14361aca6350ff7907b0e9903c7b94dc7d5d4a0Affected

LinuxLinux

3.18Affected
before 3.18Not affected
5.10.271 through 5.10.*Not affected
5.15.222 through 5.15.*Not affected
6.1.189 through 6.1.*Not affected
6.6.158 through 6.6.*Not affected
6.12.111 through 6.12.*Not affected
6.18.53 through 6.18.*Not affected
7.1.8 through 7.1.*Not affected
7.2 and laterNot affected

References

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